Tetrachloronickelate is the metal complex with the formula iCl₄sup>2−. Salts of the complex are available with a variety of cations, but a common one is tetraethylammonium. (Et4N)2NiCl4

When concentrated lithium chloride and nickel chloride solution in water is mixed, only a pentaaquachloro complex is formed: i(H₂O)₅Clsup>+. However in other organic solvents, or molten salts the tetrachloronickelate ion can form. Nickel can be separated from such a solution in water or

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is ...

, by partitioning it into a cyclohexane solution of amines. Organic ammonium salts of the type (R₃NH)₂ iCl₄are often thermochromic (R = Me, Et, Pr). Near room temperature, these salts are yellow , but these solids become blue when heated to near 70 °C. The bright blue color is characteristic of tetrahedral iCl₄sup>2−, the intensity being a consequence of the Laporte selection rule. The yellow color results from a polymer consisting of octahedral Ni centers. The corresponding tetrabromonickelates are also thermochromic with a lower transition temperatures.

History

The blue colour due to the tetrachloronickelate ion was first observed in 1944 when Remy and Meyer melted cesium chloride and cesium nickel trichloride together.

Compounds

Related substances

* tetrabromonickelates

References

{{chlorine compounds Nickel complexes Inorganic chlorine compounds Chlorometallates